Bakare: modern and simple, yet efficient backup solution

This is pre-alpha, contributions welcome

It does not even have a standalone binary yet, but the engine looks promising. Contributions are welcome :)

Goals for bakare:

Nice to haves:

Implementation notes

Motivation: All the backup systems I tried are either slow or crashing or both for me

```text --------------[ Backup Statistics ]-------------- StartTime 1547198362.85 (Fri Jan 11 09:19:22 2019) EndTime 1547209509.04 (Fri Jan 11 12:25:09 2019) ElapsedTime 11146.19 (3 hours 5 minutes 46.19 seconds) SourceFiles 3065438 SourceFileSize 585041709586 (545 GB) NewFiles 0 NewFileSize 0 (0 bytes) DeletedFiles 0 ChangedFiles 0 ChangedFileSize 0 (0 bytes) ChangedDeltaSize 0 (0 bytes) DeltaEntries 0 RawDeltaSize 0 (0 bytes) TotalDestinationSizeChange 111 (111 bytes)

Errors 0

--- Finished state OK at 12:25:15.000 - Runtime 03:06:43.000 --- ```